Nitrogen-free rinse cycle fabric softeners based on microemulsions

ABSTRACT

Anionic microemulsions of hydrophobic, normally liquid, oxygenated, long chain hydrocarbons have been found to provide nitrogen-free rinse cycle fabric softener compositions. Fatty acid esters of polyols, such as triglycerol diisostearate and sorbitan isostearate, are preferred softeners especially when microemulsified with an anionic surfactant, a cosurfactant and optionally a nonionic surfactant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to nitrogen-free rinse cycle fabric softeners andmore particularly to said softeners in the form of microemulsions whichupon dilution with water release hydrophobic materials. Thesehydrophobic materials can be long chain oxygenated hydrocarbons, such aslong chain esters, polyols and the like.

2. Description of Related Art

Fabric softening compositions and articles have long been employed tomake washed laundry items softer to the touch and more comfortable tothe wearer. Such compositions include solutions, emulsions, andparticulate and powder products. Fabric softening articles include paperstrips that have been impregnated with fabric softening compositions.Until recently, most of the commercially available rinse cycle fabricsofteners were based on quaternary ammonium salts referred to broadly asQuats. These Quats are very hydrophobic, cationic surface-active agents.A commonly used example is dimethyl ditallowyl ammonium chloride. Nowhowever these Quats are being banned from use because of ever increasingenvironmental restrictions.

Emulsions of fabric softening agents have been added to the rinse waterof washing machines to soften laundry articles. Alternatively, suchagents have been added to the wash water together with a detergentcomposition or the detergent composition can include a softeningcomponent to provide a "softergent". Fabric softening components, suchas Quats, provide softening to fabric sheets in an automatic laundrydryer during tumbling in a heated environment.

The Quats may be represented by the formula: ##STR1## wherein R, R', R",and R'" are all alkyl groups, with at least one such alkyl groups beinga higher alkyl having at least about eight carbon atoms and with therest being lower alkyls having one or two carbon atoms, and with X⁻being a salt forming anion. The preferred Quats have been quaternaryammonium salts of di-lower alkyl and di-higher alkyl ammonium halidesalthough mono-lower and tri-higher alkyl ammonium halides have also beenused.

In addition to contributing to environmental problems, the Quats haveother undesirable properties that militate against their use. Forexample, being cationic, they tend to react with anionic materials andthereby negate their intended fabric softening function. Moreover, theyare not as readily biodegradable as is desirable. They also have beenfound to be toxic to aquatic organisms leading to harmful effects onaquatic life in lakes, rivers and other into which waste waters carryingsuch compounds might be emptied.

In past efforts to find replacements for quaternary ammonium salts asfabric softeners, such candidates as neoalkanamides, glyceryl esters,silicones, cationic-anionic complexes, bentonite and various lubricantshave been suggested alone or in conjunction with quaternary ammoniumsalts. These measures have not been satisfactory because of a diminutionof the softening effects or because they introduced other undesirableproperties to the softening compositions.

In order to be efficient, a softening composition must fulfill at leasttwo conditions. These compositions must:

(1) exhibit physical and chemical stability during storage in warehousesand on store shelves. Physical stability is defined herein to mean thatno phase separation can occur.

(2) release the active softening ingredients, during the laundry rinsecycle, so that they deposit on the laundered fibers within a reasonabletime.

Several attempts have previously been made to meet these conditions andto solve the drawbacks of the known fabric softening systems.

U.S. Pat. No. 3,928,212 describes softening agents which are polyhydricalcohol esters.

U.S. Pat. No. 4,126,562 mentions erythritol and pentaerythritol whichmay be reacted with higher fatty acids to produce fabric softeners.

It is therefore an object of this invention to provide rinse cyclefabric softeners that are nitrogen free.

It is another object to provide such nitrogen-free softeners in aphysical form that renders them physically and chemically stable.

It is a further object that such softeners upon dilution with waterbecome quickly available for deposition on fiber surfaces.

Still another object is to provide nitrogen-free softeners that meetenvironmental standards including biodegradability.

Other objects will become apparent to those skilled in the art upon afurther reading of the specification.

SUMMARY OF THE INVENTION

Nitrogen-free rinse cycle softener compositions have been found meetingthe objects supra comprising an anionic microemulsion of a hydrophobic,normally liquid oxygenated long chain hydrocarbon. The term "anionicmicroemulsion" is used to mean a microemulsion comprising at least oneanionic surfactant. By normally liquid is meant liquid at ambient roomtemperature. These hydrophobic, normally liquid oxygenated hydrocarbonsmay be fatty esters of polyols, fatty alcohols, fatty acids or fattyethers. The term "fatty" refers to long chain hydrocarbon moietieshaving about 12 to about 22 carbon atoms. The preferred oxygenatedhydrocarbons used in this invention are fatty ester polyols where thepolyol moiety contains two or more hydroxyl and carbon atoms and atleast one hydroxyl group is esterified with a fatty acid containing 12to about 22 carbon atoms. While the preferred oxygenated hydrocarbonsare fatty ester polyols, the use of anionic microemulsions of C12-C14fatty alcohols, has also been demonstrated as being effective forsoftening under standard laboratory conditions.

Exemplary fatty acids include the saturated fatty acids: lauric acid,tridecylic acid, myristic acid, pentadecylic acid, palmitic acid,margaric acid, stearic acid, nondecylic acid, arachidic acid, behenicacid and the like. Unsaturated acids that can be used include:dodecylenic acid, palmitoleic acid, oleic acid, recinoleic acid,petroselinic acid, vaccenic acid, linoleic acid, eleostearic acid,licanic acid, parinaric acid, tariric acid, gadoleic acid, arachadonicacid, cetoleic acid, erucic acid, and the like.

In addition to the normal fatty acids delineated above, one may also usevarious isomers thereof in which the hydrocarbon moieties are branchedrather than straight chained as well as mixtures of fatty acids.Commercially available U.S.P. stearic acid, for example, contains amixture of stearic acid and palmitic acid.

Two particularly preferred classes of polyols are triols, such as,glycerol as well as dimers or trimers thereof including diglycerol andtriglycerol and hexitols, such as, sorbitol, mannitol, iditol, dulcitol,talitol and the like. Anhydrides of hexitols, such as sorbitan areparticularly preferred.

Other polyols useful in the practice of this invention are penitols,such as, xylitol, arabitol, adonitol, and the like.

Aldoses or sugars, such as, glucose, mannose, gulose, or idose andketoses, such as, fructose, sorbose, tagatose, and the like can also beused.

Two preferred nitrogen-free softeners are triglycerol diisostearate andsorbitan monoisostearate. These are commercially available respectivelyfrom Henkel Corp. as Emerest 2462 and ICI Specialty Chemicals as Arlacel987. Others can easily be synthesized by esterifying one or more of thefatty acids enumerated above with any of the polyols shown above in thepresence of an acid or related catalyst.

Other preferred nitrogen-free softeners include: oleate and soft tallowderivatives of sorbitan, pentaerythritol, glycerol and other polyols.

Microemulsions of the above-described oxygenated hydrocarbons areprepared by first dispersing an anionic surfactant (for example themagnesium salt of paraffin sulfonate) in water and then mixing thisdispersion with an electrolyte (such as, magnesium sulfate), a softener(such as, triglycerol diisostearate), a cosurfactant (such as, ethyleneglycol monobutyl ether), and optionally a nonionic surfactant (a fattyalcohol ethoxylate containing about 5 to about 11 ethoxy groups). Thisformation of a microemulsion is carried out at room temperature withconventional mixers or agitators in commonly used laboratory, pilotplant or production reaction vessels.

Although in the preparation of the microemulsions of this invention itis preferred to employ about 2 to about 40% oxygenated hydrocarbonnitrogen-free softener, about 2 to about 30% anionic surfactant, from 0to about 7% of an electrolyte, about 2 to about 30% of a cosurfactantand optionally from 0 to about 20% of a nonionic surfactant, it ispreferred to use about 5 to about 20% oxygenated hydrocarbonnitrogen-free softener, about 4 to about 14% anionic surfactant, from 0to about 3% of an electrolyte, about 6 to about 8% of a cosurfactant andoptionally from 0 to about 5% of a nonionic surfactant the balance, tobring the total to 100%, being water.

Representative anionic surfactants in addition to those mentioned aboveare: C10-C16 alkyl or alkylbenzene sulfonates or sulfates.Representative cosurfactants include: (poly)ethylene glycol ethers,(poly)propylene glycol ethers and alcohols.

Representative nonionic surfactants include: C9-C11 fatty alcoholethoxylates containing about 5 ethoxy groups, C12-C15 fatty alcoholethoxylates containing about 7 ethoxy groups and the like. The role ofthe surfactant-cosurfactant entity is critical since the combinationmust serve the double function of first microemulsifying thenitrogen-free softener and later releasing it onto the textile fibersupon dilution with water. This release of the softener necessitates adestabilization or breaking of the microemulsion to effect as complete adeposition of softener on fabric as possible. If this action is tooslow, softener remains microemulsified and is discarded with the rinsewater. However the ideal state is not imperative in order to provide acommercial product.

FIG. 1 is a ternary diagram showing the microemulsification of sorbitanisostearate.

FIG. 2 is a ternary diagram showing the microemulsification of sorbitanisostearate sans Mg sulfate.

FIG. 3 is a kinetics graph of microemulsion flocculation.

FIGS. 4, 5 and 6 are ternary diagrams showing the microemulsification oftriglycerol diisostearate.

The invention is further described in the examples which follow. Unlessotherwise specified, all parts and percentages are by weight.

EXAMPLE 1 Preparation of Softener Microemulsions

Varying amounts of the following components were mixed at roomtemperature in conventional laboratory flasks with agitation:

(1) 1-10% of the anionic surfactant, magnesium paraffin sulfonate (MgPS)

(2) 1-10% Of the cosurfactant, ethylene glycol monobutyl ether (EGMBE)

(3) 0-9% of the nonionic surfactant, Dobanol 91-5, a C9-C11 fattyalcohol ethyoxylate containing 5 ethoxy groups (C9-C11 E5)

(4) 5% sorbitan isostearate (SIS) and

(5) remainder 84% water.

Although the order of addition of the ingredients is not critical, theMgPS was added to the water first because it is the most difficult todisperse.

The EGMBE is available from BP Chemical Co., Shell Chemical Co. or ICISpecialty Chemicals Co.

The C9-C11 E5 was obtained from Shell Chemical Co. Dobanol 91-5.or canbe synthesized by the oxyalkylation of a C9-C11 fatty alcohol asexplained in The Encyclopedia of Polymer Science and Technology, Vol. 6,Pgs. 108-109, John Wiley and Sons Inc., NYC, 1967 incorporated herein byreference.

The SIS is commercially available from ICI Specialty Chemicals asARLACEL 987 and has the structure: ##STR2## The various combinations ofthe components were then observed to determine which affordedmicroemulsions. These data are presented in Table 1. A plot of thesedata as discrete points is shown in FIG. 1 as a ternary diagram. Thisfigure shows combinations affording microemulsions of the softener SISat 24° C. and 30° C.

                  TABLE 1                                                         ______________________________________                                        Composition (%)                                                                      C9-                                                                    MgPS.sup.(1)                                                                         C11E.sub.5.sup.(2)                                                                     EGMBE.sup.(3)                                                                           SIS.sup.(4)                                                                         Water Product                                 ______________________________________                                        1      0        10        5     84    no test                                 2      0        9         5     84    no me.sup.(5)                           1      1        9         5     84    no me                                   3      0        8         5     84    no me                                   2      1        8         5     84    me > 30° C.                      1      2        8         5     84    "                                       4      0        7         5     84    me                                      3      1        7         5     84    me > 30° C.                      2      2        7         5     84    "                                       1      3        7         5     84    "                                       5      0        6         5     84    me                                      4      1        6         5     84    me                                      3      2        6         5     84    me > 30° C.                      2      3        6         5     84    "                                       1      4        6         5     84    "                                       6      0        5         5     84    me                                      5      1        5         5     84    me                                      4      2        5         5     84    me                                      3      3        5         5     84    me                                      2      4        5         5     84    me > 30° C.                      1      5        5         5     84    no me                                   7      0        4         5     84    me                                      6      1        4         5     84    me                                      5      2        4         5     84    me                                      4      3        4         5     84    me                                      3      4        4         5     84    me > 30° C.                      2      5        4         5     84    no me                                   1      6        4         5     84    no me                                   8      0        3         5     84    me > 30° C.                      7      1        3         5     84    me > 30° C.                      6      2        3         5     84    no me                                   5      3        3         5     84    no me                                   4      4        3         5     84    no me                                   3      5        3         5     84    no me                                   2      6        3         5     84    --                                      1      7        3         5     84    --                                      9      0        2         5     84    no me                                   8      1        2         5     84    no me                                   7      2        2         5     84    no me                                   6      3        2         5     84    no me                                   5      4        2         5     84    no me                                   4      5        2         5     84    no me                                   3      6        2         5     84    no me                                   2      7        2         5     84    --                                      1      8        2         5     84    --                                      10     0        1         5     84    no me                                   9      1        1         5     84    no me                                   8      2        1         5     84    no me                                   7      3        1         5     84    no me                                   6      4        1         5     84    no me                                   5      5        1         5     84    no me                                   4      6        1         5     84    no me                                   3      7        1         5     84    no me                                   2      8        1         5     84    no test                                 1      9        1         5     84    no test                                 ______________________________________                                         .sup.(1) magnesium salt of paraffin sulfonate                                 .sup.(2) fatty alcohol ethoxylateC9-C11[O--CH.sub.2 CH.sub.2 ].sub.5 --OH     .sup.(3) ethylene glycol monobutyl ether                                      .sup.(4) sorbitan isostearate                                                 .sup.(5) me = microemulsion                                              

The breakdown of the softener microemulsion upon dilution in the rinsecycle is a necessary condition for releasing the active ingredient(softener) onto the laundered fabrics. This is indicated by theimmediate appearance of turbidity upon dilution. This was verified byparticle size distribution analysis delineated in Table 2. The resultssuggest that the microemulsion destabilization is due both to dilutionand water hardness.

                  TABLE 2                                                         ______________________________________                                        Particle Size Analysis                                                                        Composition                                                   Composition     Mean Diameter(nm)                                             SIS  MgPS    EgMBE    NI  Neat udi Water                                                                              Tap Water                             ______________________________________                                        5    6       4        1   36   226      591                                   5    5       5        1   51   227      436                                   5    5       4        2   43   231      415                                   5    4       6        1   42   368      366                                   5    4       5        2   55   252      412                                   5    4       4        3   59   236      306                                   ______________________________________                                         NI = nonionic surfactant                                                      nm = nanometers                                                               udi = ultradeionized water                                               

EXAMPLE 2 Performance Evaluation of Softeners

The effect of microemulsification on the prototype softeners studied wasassessed. These evaluations were carried out in a laboratoryminisoftening machine on desized terry cloth towels in tap water. Theprototype softener, SIS, as a microemulsion composition was comparedwith a reference Control A containing the microemulsification systemwith no softener. A test panel of 18 judges evaluated, in pairedcomparisons, swatches treated with the prototype and a Control forsoftness. Reference results, presented in Table 3 below, demonstrate thesuperiority of SIS in microemulsification form.

                  TABLE 3                                                         ______________________________________                                        Preference Evaluation                                                                         Test Panel's Evaluation                                       Composition       Proto-            Pre-                                      SIS    MgPS    EgMBE    NI  type  Control No                                                                            ference                             ______________________________________                                        a.  4.5    3.6     3.8    5.7 8     5       5                                 b.  4.4    3.6     5.7    5.7 5     10      3                                 c.  5.0    4.0     4.0    3.0 14    2       2                                 d.  5.0    4.0     6.0    1.0 14    2       2                                 e.  5.0    6.0     4.0    1.0 18    0       0                                 ______________________________________                                    

A decrease of the nonionic surfactant causes an increase in softness.The sample (e) containing the highest MgPS level displayed a highefficiency and is significantly softer than sample (c). Samples (c) and(d) were found to be equivalent in softness.

The sensitivity of the claimed microemulsions of this invention todilution and water hardness is still enhanced in nonionicsurfactant-free compositions as suggested by the particle sizedistributions presented in Table 4. When tested as above, both (f) and(h) were found to soften the terry cloth fabric significantly. Among 18judges all 18 preferred the prototype; none preferred the reference; andnone had no preference.

                  TABLE 4                                                         ______________________________________                                        Particle Size Analysis                                                                          Composition                                                 Composition       Mean Diameter(nm)                                           SIS    MgPS    EgMBE    NI  Neat udi Water                                                                             Tap Water                            ______________________________________                                        f.  5      5       6      0   63   371     1069                               g.  5      6       5      0   55   246     882                                h.  5      7       4      0   48   222     743                                i   5      6       4      1   36   226     591                                ______________________________________                                         NI = nonionic surfactant                                                      nm = nanometers                                                               udi = ultradeionized water                                               

The data above shows that the microemulsification of sorbitanisostearate tolerates wide variations in the surfactant-cosurfactantsystem compositions which govern its softening performance. Too fast adestabilization of the microemulsion has been shown to prevent thesystem from delivering a full softening efficacy.

When sodium paraffin sulfonate (PS-Na) is used as the anionic surfactantwithout introducing magnesium sulfate, the microemulsion area obtainedin Example 1 is much less sensitive to room temperature. This providesgreater flexibility of formulation. As shown in FIG. 2 it then isshifted towards lower EGMBE levels.

In the absence of nonionic surfactant, the turbidity of thesemicroemulsions only gradually appears after dilution with water as shownin FIG. 3. Samples containing nonionic surfactant even remain clear upontap water addition. The presence of magnesium sulfate with or withoutnonionic detergent results in fast turbidity. The absence of bothmagnesium and nonionic detergent results in slow turbidity. The presenceof nonionic detergent with no magnesium sulfate results in no turbidity.FIG. 3 is a plot of average particle size of the emulsion that forms(accompanied by the appearance of turbidity) versus time. When turbidityappears we no longer have a microemulsion (which is crystal clear) butan emulsion with greater particle size and a milky appearance. FIG. 3thus demonstrates the kinetics of paraffin sulfonate based microemulsionflocculation in tap water.

The microemulsion area and behavior is not much affected by the natureof cations in solution. Sodium, ammonium, and caesium cations areequivalent. Mg²⁺ interacts more strongly with the negatively-chargedhead of the surfactant, making the surfactant more hydrophobic. Otherions act by increasing the ionic strength, thus making the surfactantslightly more hydrophobic, or by improving the solubility of thesurfactant ("salting-in" effect). The salting-in efficiency variesaccording to the following sequence: Na<K<NH₄ <Cs<Mg<Ca. Other cationsthat can be used include Group Ia and Group IIa of the Periodic Chart ofthe Elements.

Conversely the microemulsion area is very sensitive to the kind ofanions present. A salting out anion, such as sulfate, gives a much widerarea than the neutral chloride anion.

The softening of swatches rinsed with SIS/PS/EGMBE/NI in a ratio of5:7:4:0 was rated 2.0 on a scale where 0 corresponds to a rinse in tapwater and 5 to a treatment with a 5% Quat emulsion (Praepagen WK fromHoechst). The rating rises to 2.5 if the rinse time is increased from 5to 30 minutes. Under the same conditions, the softening of swatchesrinsed with SIS/MgPS/EGMBE/NI in a ratio of 5:7:4:0 was rated 1.2.

EXAMPLE 3 Preparation of a Triglycerol Diisostearate Microemulsion

Using the procedure described in Example 1, a series of microemulsionsof triglycerol diisostearate (TGDiS) was prepared. TGDiS is commerciallyavailable from Henkel Corp. of Hoboken, N,J. under the trade nameEmerest 2462 and has the structure:

    R--COOCH.sub.2 --CHOH--CH.sub.2 --O--CH.sub.2 --CHOH--CH.sub.2 --O--CH.sub.2 --CHOH--CH.sub.2 --OOC--R

wherein R=C₁₇ H₃₄

Magnesium sulfate was added in the beginning of the formulation.

A systematic investigation showed that a wide microemulsion area existsin the domain of 1-8% MgPS, 2-9% EGMBE, and 0-5% C9-C11 fatty alcoholethoxylate containing 5 ethyoxy moieties. This is delineated in FIG. 4.The microemulsion area is slightly modified when the nonionic surfactantdegree of ethoxylation is increased from 8 to 12. If the magnesiumsulfate is not added to these compositions, the microemulsion arearemains wide and is displaced toward the PS apex in FIG. 6.

EXAMPLE 4 Preparation of a Fatty Alcohol Microemulsion

Using the procedure described in Example 1, a microemulsion of acommercially available C12-C14 fatty alcohol was prepared. The resultantmicroemulsion comprised 5% fatty alcohol, 4% paraffin sulfonate, 1.5%MgSO4.7H₂ O, 6% hexylene glycol butyl ether, 3% ethylene glycol butylether and the remainder water. A second composition was preparedidentical to the first with the exception that no fatty alcohol wasincluded. A performance evaluation using the procedure described inExample 3 was performed. A panel of 10 judges preferred themicroemulsion containing the fatty alcohol to that containing none.

Those skilled in the art will appreciate that the data presented supraillustrate the preparation of the first fully nitrogen-free fabricsoftener compositions in the form of a microemulsion and theirutilization in the delivery of softness to fabrics.

These softener compositions may also contain additives, such as acrylatepolymers or maleic anhydride-alkyl vinyl ether copolymers, perfumes,colorants, light stabilizers, whiteners, anti-static agents,bacteriostatic agents, and the like.

Although the test data shown employed desized terry cloth for thedemonstration of the utility of the claimed softeners, this invention isnot limited to this fabric. Other fabrics may be softened with saidsofteners including but not limited to cotton and cotton-containingitems and the like.

These microemulsions provide for the first time a method of delivering asignificant amount of active softeners to fabrics in very soft water.All previous systems require a significant level of hardness in the washor rinse water to be fully efficient.

Another advantage of these microemulsions is that they permit the userto disperse very high concentrations of active softeners (about 20%) tothe laundered fabric.

Still another facet of these microemulsions is their clarity whichcarries the concept of mildness to the user hence increasing theircommercial acceptance.

Although the invention has been described with a certain amount ofparticularity, it is understood that the present disclosure of thepreferred forms has been made only by way of example and that numerouschanges and modifications can be resorted to without departing from thespirit and scope of the invention.

What is claimed is:
 1. Method of preparing a nitrogen-free rinse cyclesoftener composition which comprises mixing at ambient roomtemperature:(A) water; (B) from 0 to about 7% of an electrolyte; (C)about 2 to about 30% of an anionic surfactant; (D) about 2 to about 30%of a cosurfactant; (E) about 2 to about 40% of a fatty acid polyolester; and (F) from 0 to about 20% of a nonionic surfactant; wherein theamount of water is sufficient to bring the total composition to 100%. 2.Method claimed in claim 1 wherein the fatty acid polyol ester istriglycerol diisostearate.
 3. Method claimed in claim 1 wherein thefatty acid polyol ester is sorbitan isostearate.
 4. Method claimed inclaim 1 wherein the anionic surfactant is a paraffin sulfonate. 5.Method claimed in claim 1 wherein the cosurfactant is an alkylene glycolmonoalkyl ether.
 6. Method claimed in claim 1 wherein the nonionicsurfactant is a fatty alcohol ethoxylate containing about 5 to about 11ethoxy groups.
 7. Method claimed in claim 1 wherein the electrolyte ismagnesium sulfate.